*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  a{
    display: block;
    text-decoration: none;
    /* // 继承父元素的字体颜色  div一样  */
    color: inherit;
  }
  img{
    /* // 3px */
    display: block;
    /* // 让图片的大小由父元素来控制 */
    width: 100%;
  }
  
  ul{
    list-style: none;
  }
  
  .clearfix::after{
    content: "";
    display: block;
    height: 0;
    line-height: 0;
    visibility: hidden;
    clear: both;
  }
  input,button{
    border: none;
    outline: none;
  }
  .fl{
    float: left;
}
.fr{
    float: right;
}